CD47 Deficiency in Mice Exacerbates Chronic Fatty Diet-Induced Steatohepatitis Through Its Role in Regulating Hepatic Inflammation and Lipid Metabolism.

Hui-Chao Tao,Yang Zheng,Bo Chen,Wai-Ou Zhao,Xue Wang,Yong-Guang Yang,Ke-Xin Chen

doi:10.3389/fimmu.2020.00148

Abstract

Inflammation is one of the hallmarks of non-alcoholic steatohepatitis. CD47 is a widely expressed transmembrane protein that signals through inhibitory receptor signal regulatory protein α (SIRPα) to inhibit macrophage activation and phagocytosis. In this study, we sought to investigate the role of CD47 in hepatosteatosis and fibrosis induced by a chronic high-fat diet (HFD), by comparing disease development in wild-type (WT) and CD47KO mice fed HFD for 40 weeks. The HFD induced remarkably more severe hepatic steatosis and fibrosis but less body weight gain and less subcutaneous fat accumulation in CD47KO mice compared to WT mice. Liver tissues from HFD-fed CD47KO mice exhibited enhanced inflammation characterized by increased proinflammatory cytokine production and increased nuclear factor-κB (NF-κB) activation compared to similarly fed WT mice. Although higher expression of apolipoproteins was observed in CD47KO mice compared to WT mice under a low-fat diet (LFD), HFD-fed WT and CD47KO mice showed comparably prominent downregulation of these apolipoprotein genes, suggesting that the marked difference observed in lipid accumulation and hepatosteatosis between these mice cannot be explained by changes in apolipoproteins. Like apolipoproteins, sirtuin 1 (SIRT1) and peroxisome proliferator activated receptor alpha (PPARα), which are involved in regulation of both lipid metabolism and inflammation, were more highly expressed in CD47KO than WT mice under LFD but more severely suppressed in CD47KO than in WT mice under HFD. Taken together, our results indicate that CD47 plays a significant role in the pathogenesis of HFD-induced hepatosteatosis and fibrosis through its role in regulation of inflammation and lipid metabolism.

Highlights

Non-alcoholic steatohepatitis (NASH) is the severe form of non-alcoholic fatty liver disease (NAFLD) characterized by excessive fat accumulation and inflammation in the liver [1, 2]
These data indicate that CD47 deficiency augments high-fat diet (HFD)-induced hepatomegaly and liver injury but suppresses subcutaneous fat accumulation and the associated increase in body weight, suggesting that CD47 plays an important role in lipid metabolism and/or distribution
We showed that CD47KO mice chronically fed HFD developed severe hepatomegaly and hepatic injury but no subcutaneous fat accumulation compared to WT mice fed HFD

Summary

Introduction

Non-alcoholic steatohepatitis (NASH) is the severe form of non-alcoholic fatty liver disease (NAFLD) characterized by excessive fat accumulation and inflammation in the liver [1, 2]. Activation of proinflammatory factors, such as the transcription factor nuclear factor-κB (NF-κB), a key regulator of inflammation, plays an important role in the progression of NASH [3]. CD47–SIRPα pathway activation provides inhibitory signaling in monocytes and macrophages, attenuating phagocytosis and inflammation [9,10,11]. This pathway may become even more important in controlling macrophage activation under inflammatory conditions [12] and after allogeneic or xenogeneic transplantation [10, 13,14,15]. Because inflammation is a key factor driving the progression of NASH, it is imperative to understand the precise role of CD47 in the pathogenesis of NASH

Methods

Results

Conclusion